The invention relates to rotary-to-linear actuators of the general type disclosed in U.S. Pat. No. 3,713,932, issued Jan. 30, 1973, and in U.S. Pat. No. 4,282,764 issued Aug. 11, 1981, which patents are incorporated herein by reference and which patents constitute prior art.
In U.S. Pat. No. 4,282,764, an external metallic helical hexagon thread form is employed, which thread form is required to be machined, which machining is excessively costly.